Composite number refers to the number divisible by other numbers (except 0) except 1 and itself in natural numbers. In contrast, it is a prime number, and 1 is neither a prime number nor a composite number. The smallest composite number is 4. Among them, the perfect number and the number of blind dates are based on this.

Factorization can be divided into two types. One is that only 1 multiplies itself, such as 1, 2, 3, 5,.

The other is that there are other ways to decompose factors besides 1 multiplying itself, such as 4, 6, ... This number is called composite number, and the word composite number means "composite and decomposable".

Therefore, a composite number is an integer that is decomposed into 1 and multiplied by itself.

Extended data

Applications: Composite Numbers and Prime Numbers

Exchange the position of a three-digit unit number with a hundred digits to get a new three-digit number. It is known that the product of these two three digits is equal to 52605, so the sum of these two three digits is 606.

Analysis: first decompose the prime factor, then recombine the prime number, and determine two three-digit numbers and then sum.

1, factorize prime factors

52605=3×3×5×7× 167

2. Prime recombination

3×3×5×7=3 15≠76 1, so it is excluded.

3×3×5=45 is a two-digit number, so it is excluded.

3×3×7=63 is a two-digit number, so it is excluded.

3×5×7= 105, at this time 3× 167=50 1, which is in line with the meaning of the question.

3. Sum

105+50 1=606

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